Ritterbrüder aren't the TO's greatest strength, that would be the Order Spearmen. T2(!) Castle(also good since the order is castle only), high stamina, large shielded, good morale, anti cavalry troops with moderate-high attack and OBSCENE defense. They hold up in a fight against everybody's T5 units except for the obvious uber units and even then they tend to shred even the best cavalry.
The best part: they are even cheaper and easier to mass produce then genoese crossbow militia. Screw all those fancy knights that require you to jump through several hoops to get and go Red Army on them, except with(most likely) superior troops.
Speaking of the Teutonic Order campaign, did anybody notice that their music is completely badass?
http://www.youtube.com/watch?v=bCHSreFMkXwhttp://www.youtube.com/watch?v=CgnVEU2ZzTIAlso, byzantine flamethrowers are balanced by only appearing in the crusades campaign, being only recruit able in constantinople, which is located in arse nowhere for that scenario and you are likely to loose it because of those damn venetian backstabbers, having the unit size of an artillery crew, being hideously expensive and their inability to be retrained anywhere other then that backwater in the corner of the map on the far side of a sea which is right besides he spawning point for all scripted baddies.
A word of warning about artillery, the manogel rains fiery death upon enemies
between itself and the target. Never, ever use your general's bodyguard to screen your siege equipment from enemy charges if you deploy those. Don't forget to reposition them so that they never shoot over your own troops too if a fight breaks out. Even better, use trebuchets instead. They do produce very pretty fireworks in custom night battles however.
Also, if you have a non steam and unpatched version of kingdoms, try some using some lithuanian arqebusiers against anything else in a custom battle.